Free burn rate in reference to cigarettes and the like relates to the rate at which the coal or burning ember of a lit cigarette advances along the cigarette when the cigarette is not being smoked. Considerable thought has been given to free burn rate of a cigarette from the standpoint of reducing sidestream smoke generated during the idle phase of the lit cigarette. Various cigarette tobacco and cigarette paper designs have been suggested which, in one way or another, affect free burn rate with a view to reducing sidestream smoke and/or achieving an extinguishment of the lit cigarette when left idle over an extended period of time. Such designs include a judicious selection of tobacco blends, densities and multiple layers of cigarette tobacco in the tobacco rod. Such selection can appreciably retard the free burn rate of the cigarette and hence increase the number of puffs obtained per unit length of cigarette. Either in combination with tobacco selection and construction, or independently of the tobacco make-up, various cigarette paper compositions can also affect free burn rate of the cigarette. Such paper compositions include the use of chemicals to retard free burn rate, multiple wrappings of different types of cigarette paper of the same or different characteristics and reduction of cigarette paper air permeability. In addition to the use of chemicals to extinguish a cigarette when not being smoked, there are a variety of cigarette extinguishing devices. A cigarette ashtray may have a well dimensioned to receive the lit end of the cigarette, such that when the lit end of the cigarette is positioned in the well, the supply of oxygen to the burning coal is substantially reduced such that the cigarette extinguishes very quickly. Another approach to achieve extinguishment of the cigarette is to provide on the cigarette a ring of combustible or meltable material which releases into the tobacco upon melting at the temperature of the burning coal a suitable chemical for immediately extinguishing the cigarette.
Exemplary patents which describe designs in keeping with the above-noted approach in modifying tobacco and paper make up include published EP application 540,361, published May 5, 1993, published EP application 495,567 published Jul. 22, 1992, Canadian Patent 1,259,008 Canadian Patent 1,223,495 Canadian Patent 1,211,021 and Canadian patent 1,300,459.
An approach to reducing the possibility of a burning cigarette starting fires, is to house the cigarette in a screen mesh as described in U.S. Pat. No. 4,194,516. The screen mesh houses the burning portion of the cigarette to thereby contain any sparks and the like which may come off of the cigarette during the smoking process. Although this device may reduce the chances of starting a fire with a lit cigarette, it does not affect the free burn rate of the cigarette, because the screen is of an open mesh design.
French patent 2,556,184 describes a device which may be mounted on a cigarette to extinguish the cigarette at a predetermined location along its length. The device is designed to automatically and completely extinguish the cigarette when the advancing burning coal in the cigarette approaches the device. The device is in the form of a ring which is capable of being moved to any location along the cigarette. The ring is made of a material which melts to release an extinguishing agent which immediately extinguishes the burning end of the cigarette by penetrating the tobacco through to the burning coal. The extinguishing agent may include a perfume so as to avoid a disagreeable odor at the moment when the cigarette is extinguished. Although this device is effective for extinguishing a cigarette, it is not reusable and in being consumed and releasing a perfume into the cigarette, it does not permit re-smoking of the extinguished cigarette.
Another type of extinguishing ring is described in respect of the ash-retaining screen for a cigarette of U.S. Pat. No. 1,211,071. A cigarette or the like is contained in a cage which consists of a screen to effectively confine the ashes and at the same time admit an abundance of fresh air to support combustion. Provided on the exterior of the screen cage is a flame extinguishing collar which is slidable upon the ash-retaining cage and is adapted to be seated at any desired point along the length of the cage for the purposes of extinguishing the cigarette when partially consumed. This device contemplates relighting the cigarette for further consumption. However, neither the device of this U.S. Patent or that of French Patent 2,556,184 contemplates a device which may be used on a cigarette to reduce sidestream smoke from a free-standing lit cigarette.
U.S. Pat. No. 4,638,819 describes a device for decreasing sidestream smoke generated by a lit cigarette. The device has a hole through which the cigarette is inserted. The device permits continuous combustion of the cigarette but limits the quantity of oxygen supplied to the burning ember thereby preventing generation of sidestream smoke when the lit cigarette is sitting idle. The device is moved along the cigarette as the burning ember advances. Several problems are however associated with this type of device. One of the major problems is staining of the cigarette, which results in an unsightly cigarette as the device is moved therealong. Varying diameters in cigarettes do not provide for precise control in the flow of air to the burning ember and hence the device can have a variable effect in decreasing sidestream smoke.
U.S. Pat. No. 5,055,230 describes a smoker's appliance which includes a cigarette receptacle which is capable of reducing quantity of smoke emitted from a lit cigarette while the cigarette is idle. The device includes a hole into which the lit cigarette may be inserted. The hole is polygonal is cross-section. The purpose of the receptacle is to conduct heat away from the burning ember and as well minimize air circulation which could upset the slow burning of the cigarette when in its dormant state. The receptacle does not extinguish the cigarette immediately, but will allow the cigarette to continue to burn at a very slow rate without producing smoke for several minutes. Like the device of U.S. Pat. No. 4,638,819, the cigarette receptacle of solid wall construction causes considerable staining and due to variable cigarette diameters, cannot always reliably provide the desired degree of sidestream smoke reduction and extinguishing times.
U.K. patent specification 928,089 describes a combustion control device for cigarettes which has for its purpose to control the rate at which a cigarette burns, thereby extending the length of time the cigarette is smoked. The control tube has a plurality of apparatus or the like which may be adjusted to control the rate at which air reaches the burning end of the cigarette. In the alternative, crimpings may be provided in the control tube to control flow of air to the burning end. However, such crimping suffers from the same problem an that of U.S. Pat. No. 4,638,819 in not reliably providing the desired control of cigarette burn rate. The control tube is lined with metal foil which can lead to unsightly staining of the cigarette during smoking. The user of the control tube has considerable choice in respect of controlling cigarette burn rate by varying the size of aperture opening, hence, further unreliability in controlling free-burn rate of the cigarette without any consequent control of sidestream smoke.